Устаревший алгоритм безопасности беспроводных сетей WEP

Deprecated security algorithm for wireless networks
Wired Equivalent Privacy (WEP) is a severely flawed security algorithm for 802.11 wireless networks. Introduced as part of the original IEEE 802.11 standard ratified in 1997, its intention was to provide data confidentiality comparable to that of a traditional wired network. WEP, recognizable by its key of 10 or 26 hexadecimal digits (40 or 104 bits), was at one time widely used, and was often the first security choice presented to users by router configuration tools. Subsequent to a 2001 disclosure of a severe design flaw in the algorithm, WEP was never again secure in practice. In the vast majority of cases, Wi Fi hardware devices relying on WEP security could not be upgraded to secure operation. Some of the design flaws were addressed in WEP2, but WEP2 also proved insecure, and another generation of hardware could not be upgraded to secure operation. In 2003, the Wi Fi Alliance announced that WEP and WEP2 had been superseded by Wi Fi Protected Access (WPA). In 2004, with the ratification of the full 802.11i standard (i. e. WPA2), the IEEE declared that both WEP 40 and WEP 104 have been deprecated. WPA retained some design characteristics of WEP that remained problematic. WEP was the only encryption protocol available to 802.11a and 802.11b devices built before the WPA standard, which was available for 802.11g devices. However, some 802.11b devices were later provided with firmware or software updates to enable WPA, and newer devices had it built in.

WEP was ratified as a Wi Fi security standard in 1999. The first versions of WEP were not particularly strong, even for the time they were released, due to U. S. restrictions on the export of various cryptographic technologies. These restrictions led to manufacturers restricting their devices to only 64 bit encryption. When the restrictions were lifted, the encryption was increased to 128 bits. Despite the introduction of 256 bit WEP, 128 bit remains one of the most common implementations.

WEP was included as the privacy component of the original IEEE 802.11 WEP uses the stream cipher RC4 for confidentiality, and the CRC 32 checksum for integrity. It was deprecated in 2004 and is documented in the current standard. Standard 64 bit WEP uses a 40 bit key (also known as WEP 40), which is concatenated with a 24 bit initialization vector (IV) to form the RC4 key. At the time that the original WEP standard was drafted, the U. S. Government's export restrictions on cryptographic technology limited the key size. Once the restrictions were lifted, manufacturers of access points implemented an extended 128 bit WEP protocol using a 104 bit key size (WEP 104). A 64 bit WEP key is usually entered as a string of 10 hexadecimal (base 16) characters (0–9 and A–F). Each character represents 4 bits, 10 digits of 4 bits each gives 40 bits; adding the 24 bit IV produces the complete 64 bit WEP key (4 bits × 10 + 24 bit IV = 64 bit WEP key). Most devices also allow the user to enter the key as 5 ASCII characters (0–9, a–z, A–Z), each of which is turned into 8 bits using the character's byte value in ASCII (8 bits × 5 + 24 bit IV = 64 bit WEP key); however, this restricts each byte to be a printable ASCII character, which is only a small fraction of possible byte values, greatly reducing the space of possible keys. A 128 bit WEP key is usually entered as a string of 26 hexadecimal characters. 26 digits of 4 bits each gives 104 bits; adding the 24 bit IV produces the complete 128 bit WEP key (4 bits × 26 + 24 bit IV = 128 bit WEP key). Most devices also allow the user to enter it as 13 ASCII characters (8 bits × 13 + 24 bit IV = 128 bit WEP key). 152 bit and 256 bit WEP systems are available from some vendors. As with the other WEP variants, 24 bits of that is for the IV, leaving 128 or 232 bits for actual protection. These 128 or 232 bits are typically entered as 32 or 58 hexadecimal characters (4 bits × 32 + 24 bit IV = 152 bit WEP key, 4 bits × 58 + 24 bit IV = 256 bit WEP key). Most devices also allow the user to enter it as 16 or 29 ASCII characters (8 bits × 16 + 24 bit IV = 152 bit WEP key, 8 bits × 29 + 24 bit IV = 256 bit WEP key).

The Caffe Latte attack is another way to defeat WEP. It is not necessary for the attacker to be in the area of the network using this exploit. By using a process that targets the Windows wireless stack, it is possible to obtain the WEP key from a remote client. By sending a flood of encrypted ARP requests, the assailant takes advantage of the shared key authentication and the message modification flaws in 802.11 WEP. The attacker uses the ARP responses to obtain the WEP key in less than 6 minutes.

Use of encrypted tunneling protocols (e. g., IPsec, Secure Shell) can provide secure data transmission over an insecure network. However, replacements for WEP have been developed with the goal of restoring security to the wireless network itself.

The recommended solution to WEP security problems is to switch to WPA2. WPA was an intermediate solution for hardware that could not support WPA2. Both WPA and WPA2 are much more secure than WEP. To add support for WPA or WPA2, some old Wi Fi access points might need to be replaced or have their firmware upgraded. WPA was designed as an interim software implementable solution for WEP that could forestall immediate deployment of new hardware. However, TKIP (the basis of WPA) has reached the end of its designed lifetime, has been partially broken, and has been officially deprecated with the release of the 802.11 2012 standard.

This stopgap enhancement to WEP was present in some of the early 802.11i drafts. It was implementable on some (not all) hardware not able to handle WPA or WPA2, and extended both the IV and the key values to 128 bits. It was hoped to eliminate the duplicate IV deficiency as well as stop brute force key attacks. After it became clear that the overall WEP algorithm was deficient (and not just the IV and key sizes) and would require even more fixes, both the WEP2 name and original algorithm were dropped. The two extended key lengths remained in what eventually became WPA's TKIP.

WEPplus, also known as WEP+, is a proprietary enhancement to WEP by Agere Systems (formerly a subsidiary of Lucent Technologies) that enhances WEP security by avoiding "weak IVs". It is only completely effective when WEPplus is used at both ends of the wireless connection. As this cannot easily be enforced, it remains a serious limitation. It also does not necessarily prevent replay attacks, and is ineffective against later statistical attacks that do not rely on weak IVs.

Dynamic WEP refers to the combination of 802.1x technology and the Extensible Authentication Protocol. Dynamic WEP changes WEP keys dynamically. It is a vendor specific feature provided by several vendors such as 3Com. The dynamic change idea made it into 802.11i as part of TKIP, but not for the WEP protocol itself.